When a website is created and put online, there is a configuration file that is automatically created on the server that hosts the website.
The DNS Records Checker allows you to check the fields in this configuration file. Notably to know the primary and secondary DNS of the site concerned (NS fields), to know the mail configuration (field MX). To simplify, this tool allows you to check all the fields configured in the configuration file of a site (A, CNAME, NS, MX, SPF, TXT ...)
The DNS checker is free and you can use it as many times as you like.